Boom sheave assembly

ABSTRACT

A boom sheave assembly is provided wherein a sheave shaft is supported by a plurality of struts which are loaded substantially only in tension. The boom sheave assembly is pivotally mounted to position a beam, strong in bending, in alignment with the direction of the forces applied to a load implement.

United States Patent Pech [ 51 Aug. 1, 1972 BOOM SHEAVE ASSEMBLY [72]Inventor: David J. Pech, Manitowoc, Wis.

[73] Assignee: Manitowoc Engineering Company,

Manitowoe, Wis. [22] Filed: Dec. 30, 1969 [21] Appl. No.: 889,188

[52] US. Cl ..254/192, 212/39 [51] Int. Cl. ..B66d l/36 [58] Field ofSearch ....254/192, 194, 195; 212/3, 58,

[56] 7 References Cited UNITED STATES PATENTS 3,092,261 6/1963 Nesbit..212/39UX 3,485,383 12/1969 Beduhn ..212/48 12/1950 Gorrell ..254/192 X2,644,666 7/1953 Johnson ..254/195 X 2,902,177 9/1959 Stoddard et al..212/58 3,236,390 2/1966 Sprengel .212/3 FOREIGN PATENTS ORAPPLICATIONS 219,142 8/1968 U.S.S.R. ..212/59 Primary Examiner-RichardE. Aegerter Att0rney-G. Turner Moller [5 7] ABSTRACT A boom sheaveassembly is provided wherein a sheave shaft is supported by a pluralityof struts which are loaded substantially only in tension. The boomsheave assembly is pivotally mounted to position a beam, strong inbending, in alignment with the direction of the forces applied to a loadimplement.

4 Claims, 4 Drawing Figures 9 PATENTEUAUB 1 I972 3.680.840

sum 1 or 3 II JVENTOR DAVID J. PECH PATENTEDA B 1 9 2 3.680.840 sum 2 or3 ammniiilmiiilw 14/98 \VAIOO INVENTOR DAVID J. PECH N 2' LL PATENIEUnuc1 m2 SHEET 3 [1F 3 INVENTOR DAVID J. PECH Ll iklmll liliiiHl iiiinmiiiinliHUHHiHIH "Y GM /y BOOM SHEAVE ASSEMBLY With the advent of cranescapable of lifting substantial loads, it is necessary to increase theload handling capacity of the boom sheave assembly. Typical boom sheaveassembliesfor less heavily loaded booms comprise a plurality of sheavesmounted on a sheave shaft with the opposite ends of the sheave shaftmounted on the boom. The most elementary approach taken by the prior artto increase the load bearing capacity of a boom sheave assembly has beento increase the size of the sheave shaft to handle the larger loads.

Along with the trend to greater crane capacities, it has been thepractice to increase the number of lines between the boom sheaveassembly and a traveling block. There have consequently been moresheaves mounted on the sheave shaft thereby necessitating a longer shaftto accommodate the additional sheaves. Longer sheave shafts haveaggravated the bending of the shaft. It will be apparent that increasingthe diameter of the sheave shaft to accommodate greater loads andparticularly to accommodate greater bending loads, has obvious practicallimits.

One approach of the prior art to minimize bending of the sheave shaft isto support the sheave shaft intermediatethe ends thereof by one or morecantilevered struts. Since these struts of the prior art extend betweenthe sheaves, the struts must be relatively narrow and consequentlycannot have a substantial flange thereon imparting substantialresistance to bending. Since a cantilevered mounting is a relativelyweak securernent for a strut of this nature, this approach of the priorart has not been altogether satisfactory.

This invention comprises a boom sheave assembly having a beam parallelto the sheave shaft, which is strong in bending, with the sheave shaftbeing secured thereto by a plurality of depending struts which areloaded substantially only in tension. The beam is pivotally mounted onthe crane boom so that load forces applied to the sheaves pivot the beamto position the same coplanar with the direction of the applied loads.

It is an object of this invention to provide a boom sheave assembly ofmaximum strength consistent with low weight.

Another object of the invention is to provide a boom sheave assemblywherein a sheave shaft is supported intermediate the ends thereof by aplurality of struts stressed substantially only in tension.

A further object of the invention is to provide a boom sheave assemblycomprised of a beam to position the same in alignment with forcesapplied. to the sheaves. I

Still another object of the invention is to provide a crane having aboom thereon equipped with a sheave assembly of the aforementioned type.

IN THE DRAWINGS:

FIG. 1 is a side elevational view of a high capacity crane equipped witha boom sheave assembly of the invention;

FIG. 2 is an enlarged side elevational view of the boom sheave assemblyof FIG. 1;

FIG. 3 is a front view of the boom sheave assembly of FIG. 2, certainparts being broken away for clarity of illustration; and

FIG. 4 is a cross-sectional view of the boom sheave assembly of FIGS. 2and 3 taken substantially along line 4-4 of FIG. 3 as viewed in thedirection indicated by the arrows.

Attention is directed to FIG. 1 wherein there is illustrated a crane 10having a boom 12 pivotally mounted to a carrier 14. The carrier 14 issupported by an underlying ring 16 and is secured to an upper works 18for rotation therewith. Interconnecting the boom 12 and the carrier 14are suitable boom stops 15 which act to prevent elevation of the boom 12beyond a predetermined angle with respect to the underlying groundsurface. This type of crane is described in more detail in theapplication of Daniel E. Beduhn, Ser. No. 704,488, filed Feb. 9, 1968,now U.S. Pat. No. 3,485,383 and assigned to the assignee of thisapplication.

Secured to the free end of the boom 12 is a boom sheave assembly 20 madein accordance with this invention. A load line 22 is operativelyconnected to a drum 24 on the upper works 18 and is reeved through thesheave assembly 20 to an implement 26 illustrated as a traveling block.The path of the load line 22 is defined by a plurality of guide sheaves28 as is customary.

Referring to FIGS. 2-4, the boom sheave assembly 20 comprises as majorcomponents a load supporting beam 30, mounting means 32 for securing theassembly 20 to the boom 12, a sheave shaft 34, a plurality of sheaves 36and a plurality of struts 38 securing the shaft 34 to the beam 30.

The beam 30 is illustrated as a deep rectangular box having walls 40,42, 44, 46 secured together by suitable weldments 48. The ends of thebox beam 30 are closed by end caps 50, 52 secured by weldments 54. Thebeam 30 consequently has a major axis of bending strength 56 disposed ona radius of the sheave shaft 34 and a minor axis of bending strength 58perpendicular to the major axis 56. Although a rectangular box beam isillustrated, it will be apparent that a square box beam, an I- beam, aT-beam, a tube or any other structural member strong in bending may beused.

Referring to FIGS. 2 and 3, the mounting means 32 is illustrated ascomprising a pair of arms 60, 62 secured adjacent opposite ends of thebeam 30 and providing a pair of socket forming members 64, 66. Themembers 64, 66 are aligned with a pair of complementary socket formingmembers 68, 70 provided at the top of the boom 12 with a pair of pins72, 74 securing the socket forming members 64, 66, 68, 70 together.Suitable means, such as cotter keys or the like, may be provided toretain the pins 72, 74 in position. The members 64, 66 define a pivotaxis spaced from the shaft 34, the importance of which will be explainedhereinafter. It will be seen that the mounting means 32 not onlyconstitutes means for mounting the beam 30 and the assembly 20 on theboom 12, but also constitutes means for pivotally mounting the beam 30and the struts 38 in a manner more fully described hereinafter.

Each of the sheaves 36 comprises a suitable bearing 76 rotatablymounting the sheave 36 on the shaft 34. Suitable lubrication connections78 may be provided for the bearings 76. Annular sealing plates 80 aresecured to the hub of the sheave 36 and operate to retain lubricant inthe bearing 76. The plates 80 also act as bearings to accommodate anyrelative rotation between adjacent abutting sheaves 36. As will beapparent from the insuing description, the plates 80 also act as abearing between the struts 38 and the sheaves 36 adjacent thereto.

As shown best in FIGS. 3- and 4, the struts 38 are secured at the upperend thereof to the beam 30. The lower end of each strut 38 provides anaperture 82 closely receiving the sheave shaft 34. A pair of endfittings 84, 86 captivate the shaft 34 in the apertures 82 of the struts38. Suitable connections 88 afiix the end fittings 84, 86 to the ends ofthe shaft 34. The generally circular end fittings 84, 86 are providedwith a straight segment 90, 92 which cooperate with an abutment 94, 96affixed to the outer struts 38. It will be apparent that the segments90, 92 and the abutments 94, 96 prevent rotation of the shaft 34.

Since the sheave shaft 34 is supported at a number of spaced locationsalong the length thereof, the deflection of the shaft 34 in bending issubstantially reduced. It will be noted that the struts 38 depend fromthe beam 30 and are free from features which would induce substantialbending forces therein.

When the crane is hoisting a load in a purely vertical direction, theforces applied to the shaft 34 resolve into a vertical force vector 98shown in FIG. 2. It will be apparent that the stresses resulting in thestruts 38 are substantially only tensile in nature. It will also beapparent that the loads applied to the beam 30 are in alignment with themajor axis of bending strength 56. It will be further apparent that whenthe angle of the boom is changed, as is common in crane operation, the

boom sheave assembly 20 will remain vertical with the load in line withthe major axis of the beam 30.

It will be apparent that the crane 10 is called upon to handle otherthan purely vertical loads, for example when a load is rotated about theaxis of the upper works 18 or when a load is lifted from a locationother than immediately below the boom top. The forces applied to theshaft 34 resolve into a non-vertical force vector 100 which radiallyextends from the shaft 34. Since the pivot axis defined by the members64, 66 is spaced from the shaft 34, a counter clockwise moment isinduced in the boom sheave assembly 20 to rotate the beam 30, the struts38 and the shaft 34 to align the force vector 100 with the beam 30, thestruts 38 and the shaft 34. Without the movable connection provided bythe mounting means 34, it will be apparent that the force transmitted tothe struts 38 would not be substantially only in tension but insteadwould include a substantial bending force thereby converting the struts38 into cantilevered beams. Since the struts 38 are substantially weakerwhen mounted as a cantilevered beam rather .than as a pendant support,it will be seen that the capacity of the boom sheave assembly 20 wouldbe substantially reduced. In a similar fashion, the forces applied tothe beam 30 would no longer be in alignment with the major axis ofbending strength 56 thereby decreasing the load bearing capacity of thebeam 30 and consequently detracting from the capacity of the boom sheaveassembly 20. It will accordingly be apparent that the movable connectionprovided by the mounting means 32 is of significant utility.

lclaim:

l. A crane comprising a boom means for elevating the boom with respectto an underlying surface including means for preventing elevation of theboom beyond a predetermined angle with respect to the underlyingsurface;

a boom sheave assembly comprising a shaft having an axis; a plurality ofsheaves thereon; a beam above the shaft; a plurality of dependingstruts, connecting the beam and the shaft, substantially whollysupporting the shaft and stressed substantially only in tension inresponse to a load applied to the shaft; and means connecting the beamand the boom for pivotally mounting the sheave assembly on the boom; thepivotal mounting means including arms extending from the beam andcooperative pivotal connections, between the arms and the boom, defininga pivot axispositioned between the beam and the shaft axis;

a load line reeved over the sheaves; and

an implement operatively connected to the load line and movable withrespect to the sheave assembly for handling a load.

2. The crane of claim 1 wherein the arms and the struts reside on acommon radius relative to the shaft.

3. The crane of claim 2 wherein the beam, shaft and pivotal connectionsreside substantially in a common plane.

4. The crane of claim 1 wherein the plurality of struts includes strutsat opposite end portions of the shaft and at least one intermediatestrut connected to the shaft between two of the sheaves.

1. A crane comprising a boom; means for elevating the boom with respectto an underlying surface including means for preventing elevation of theboom beyond a predetermined angle with respect to the underlyingsurface; a boom sheave assembly comprising a shaft having an axis; aplurality of sheaves thereon; a beam above the shaft; a plurality ofdepending struts, connecting the beam and the shaft, substantiallywholly supporting the shaft and stressed substantially only in tensionin response to a load applied to the shaft; and means connecting thebeam and the boom for pivotally mounting the sheave assembly on theboom; the pivotal mounting means including arms extending from the beamand cooperative pivotal connections, between the arms and the boom,defining a pivot axis positioned between the beam and the shaft axis; aload line reeved over the sheaves; and an implement operativelyconnected to the load line and movable with respect to the sheaveassembly for handling a load.
 2. The crane of claim 1 wherein the armsand the struts reside on a common radius relative to the shaft.
 3. Thecrane of claim 2 wherein the beam, shaft and pivotal connections residesubstantially in a common plane.
 4. The crane of claim 1 wherein theplurality of struts includes struts at opposite end portions of theshaft and at least one intermediate Strut connected to the shaft betweentwo of the sheaves.